1. Technical Field
This invention relates to computer pointer control, and more particularly, to distinguishing between different pointing devices for use with a touchscreen.
2. Description of the Related Art
Computer based devices utilizing touchscreen technology have become commonplace in many facets of life. Examples can include personal digital assistants (PDAs) such as the Palm Pilot, available from Palm Computing, Inc., of Santa Clara, Calif., and computer driven kiosks for dispensing information to shoppers and other consumers. Presently, computer based devices incorporating touchscreen technology process stylus contact with a touchscreen in the same manner as finger contact with a touchscreen. For example, such computer-based devices do not distinguish a user's finger from a stylus when determining the location in the touchscreen where the contact occurred. Additionally, in the case of multiple touchscreen contacts, such computer based devices do not distinguish a finger from a stylus, particularly in regard to touchscreen parameters of duration and control.
The inability to distinguish between contact originating from a user's finger and contact originating from a stylus can be problematic. Specifically, different procedures can be used to emulate realtime on-screen pointer or cursor control based upon whether the system is to be used with a finger or a stylus. These differing procedures are largely an outgrowth of the differing physical properties associated with a stylus and a finger. One such physical property is the size of the contact area between a user's finger and the touchscreen, which is significantly larger than the contact area between a touchscreen and a stylus.
One disadvantage caused by the physical size of a finger is that the finger can obscure the view of controls displayed in the touchscreen. This is especially true of realtime on-screen pointer control systems where a finger placed upon the touchscreen can obscure the on-screen pointer. Another disadvantage caused by the size of a finger is that the selection of usually displayed objects in the touchscreen can be inexact. Specifically, although the touchscreen can detect a larger contact area, the contact is treated no differently than a stylus. Consequently, selection of objects with pixel accuracy can be cumbersome due to the large contact area resulting from finger contact with a touchscreen. Additionally, minute and unintentional movements of a finger can result in erratic movement of the on-screen cursor.
Several solutions have been developed to address the problems associated with finger initiated contact with a touchscreen as it relates to realtime on-screen pointer control. One such solution is the cursor offset solution, where the cursor is relocated a particular distance away from the detected contact point with the touchscreen. This enables the user to maintain an unobscured view of the cursor. Additionally, the visual feedback aids the user in controlling the realtime on-screen cursor.
Another solution for dealing with finger initiated contact with a touchscreen is the pause strategy. The pause strategy involves detecting a contact with a touchscreen. The contact duration is calculated to determine whether the contact was intentional. For example, contacts having a duration less than a particular threshold period of time can be interpreted as accidental. Contacts having a duration within a mid-range period of time can be interpreted as a single-click event. Two detected contacts of a particular duration occurring within a particular time frame can be interpreted as double-click events.
Still the aforementioned solutions can be ineffective because such solutions can be utilized only if a design was intended to function with finger contact rather than stylus contact. This result is primarily because the strategies for finger contact with a touchscreen hinder the simpler interaction afforded by the more precise stylus. Presently, touchscreen systems are unable to distinguish between a contact initiated by a finger and a contact initiated by a stylus. Consequently, present systems do not allow a user to freely alternate between using a stylus and a finger as a pointing device with a touchscreen.